The production of stone-coated roofing tiles involves several key raw materials, each playing a crucial role in ensuring the tiles’ durability, aesthetics, and performance. Here’s a breakdown of the main raw materials used:

1. Galvanized Steel (or Galvalume Steel)

• Material Composition: The core of the stone-coated roofing tile is typically made from steel, chosen for its strength and durability. The steel is usually a cold-rolled steel sheet, which undergoes a galvanization process to coat it with a protective layer of zinc (galvanized steel) or an aluminum-zinc alloy (galvalume steel).
• Thickness and Grade: The steel sheets used are generally around 0.4mm to 0.6mm thick. The grade of steel is important as it affects the tile’s performance under various conditions. High-quality steel with proper tensile strength ensures that the tiles are both lightweight and strong.
• Corrosion Resistance: The zinc or aluminum-zinc coating protects the steel from corrosion. The aluminum-zinc alloy (galvalume) provides superior corrosion resistance, especially in environments prone to rust, such as coastal areas. The choice between galvanized and galvalume steel often depends on the specific environmental conditions the tiles will face.

2. Acrylic Resin

• Chemical Properties: Acrylic resin is a type of plastic that is known for its clarity, durability, and resistance to weathering. It is used as a binder for the stone granules, ensuring they adhere firmly to the steel substrate.
• Application: The resin is applied in liquid form, creating a sticky surface that the stone granules can adhere to. It also acts as a sealant, protecting the steel core from moisture and UV damage.
• Durability: Acrylic resin is chosen for its excellent performance in outdoor applications. It resists yellowing and cracking under exposure to sunlight and extreme temperatures, which is crucial for roofing materials that need to last for decades.

3. Natural Stone Granules

• Source: The granules are often made from naturally occurring stone such as basalt or granite, which are chosen for their hardness and durability. The stone is crushed into small granules, typically in the size range of 0.5mm to 1.5mm.
• Color Coating: The granules are coated with ceramic or other pigments to provide a wide range of colors. These pigments are baked onto the granules at high temperatures, which helps to ensure that the colors do not fade over time due to UV exposure.
• Function: The stone granules not only give the tiles their distinctive appearance but also protect the underlying steel from UV rays and mechanical damage. They add texture to the surface, which can help reduce the noise from rain and hail, making the roof quieter than a plain metal roof.

4. Basecoat

• Composition: The basecoat is usually a blend of acrylic resin, fillers, and other chemical additives that improve adhesion and provide additional waterproofing properties.
• Function: This layer is crucial for ensuring that the stone granules adhere firmly to the steel substrate. The basecoat also adds an additional protective layer, helping to seal the steel and prevent moisture penetration.
• Application Process: The basecoat is applied after the steel has been galvanized or coated with galvalume. It is typically applied by spraying or dipping the steel sheet, ensuring an even coating that covers the entire surface.

5. Topcoat/Overglaze

• Properties: The topcoat is a clear or slightly tinted protective layer applied over the stone granules. It is often made from an acrylic or polyurethane resin, chosen for its UV stability and resistance to wear.
• Function: This layer seals the surface of the tiles, preventing water from penetrating and helping to lock the stone granules in place. It also provides additional protection against UV rays, which can cause fading or deterioration of the granules over time.
• Durability: The topcoat is designed to be highly resistant to weathering, ensuring that the roofing tiles maintain their appearance and performance over many years. It also provides a glossy finish that enhances the aesthetic appeal of the tiles.

6. Aluminum-Zinc Alloy Coating (Galvalume)

• Composition: Galvalume is a coating made from an alloy of approximately 55% aluminum, 43.4% zinc, and 1.6% silicon. This combination provides superior corrosion resistance compared to traditional galvanized coatings.
• Function: The aluminum in the alloy provides a barrier against corrosion, while the zinc offers sacrificial protection, meaning it will corrode in preference to the steel substrate. The silicon helps the coating adhere to the steel and provides additional durability.
• Advantages: Galvalume-coated steel is particularly effective in environments with high humidity, salt spray, or acidic conditions. It has a longer lifespan than galvanized steel and is often used in areas with harsh weather conditions.

Manufacturing Process Overview:

1. Steel Preparation: The steel coils are cut into sheets and then cleaned to remove any oils or impurities that could affect adhesion.
2. Coating: The steel is coated with zinc or an aluminum-zinc alloy using a hot-dip process.
3. Basecoat Application: The steel is then coated with the basecoat, which is allowed to dry before moving to the next stage.
4. Stone Granule Application: The stone granules are applied to the basecoat while it is still tacky, ensuring that they adhere properly.
5. Topcoat Application: After the stone granules have been applied, the topcoat is sprayed onto the surface to seal the granules in place.
6. Curing: The coated steel sheets are then cured in an oven to set the coatings and ensure they bond properly.
7. Cutting and Forming: Finally, the coated sheets are cut and shaped into tiles, which are then inspected for quality before being packaged and shipped.

These materials and processes combine to create stone-coated roofing tiles that are not only durable and long-lasting but also visually appealing, with a wide range of colors and styles to suit different architectural designs.